The present invention relates to a coin validator.
U.S. Pat. No. 4,474,281 discloses a coin validation apparatus wherein a pair of optical beams are directed across the coin path of a validator, substantially in the plane of a coin under test. The optical beams are spaced along the direction of travel of a coin in the coin path. The diameter of a coin is determined by timing the periods during which each of the optical beams is interrupted by a passing coin, determining a value for the speed of the coin as it crosses the beams, deriving two diameter values from the timed periods and the speed values, and averaging the resultant values. The average produced is proportional to the diameter of the coin interrupting the beams.
If the apparatus of U.S. Pat. No. 4,474,281 is to function correctly, a coin to be tested must be in free fall before it encounters the first optical beam. A problem arises from this in that it is difficult to produce a compact validator with a sufficient run-in for a coin to be in free fall, before it interrupts the first optical beam. The problem is particularly acute in the case of validators for the large tokens used in some casinos.
DE-A-2 724 868 discloses an apparatus in which the diameter of a coin is checked on the basis of the time between the leading edge of the coin reaching a lower reference and the trailing edge of the coin leaving an upper reference position. However, this apparatus suffers from two disadvantages. Firstly, a counter is started when the coin reaches the upper reference position. Consequently, the upper reference position must be located at least the diameter of the largest acceptable coin from the coin insertion slot. Secondly, the example, in which the diameter of a coin is checked on the basis of the time between the leading edge of the coin reaching a lower reference and the trailing edge of the coin leaving an upper reference position, cannot be used with coins whose diameters are not greater than the separation of the reference positions.
GBA-1 405 936 discloses a coin validation apparatus comprising means defining first and second reference positions spaced along a coin path, sensor means for detecting a trailing point on a coin passing the first reference position and a leading point on the coin reaching the second reference, and processing means for determining the velocity of a coin under test on the basis of the output of the sensor means. However, the diameter of the coin is checked using additional sensors.
In the following the term xe2x80x9ccoinxe2x80x9d means coin, token and any similar objects representing value.
It is an aim of the present invention to overcome the afore-mentioned disadvantages of the prior art.
According to a first aspect of the present invention, there is provided a coin validation apparatus comprisingmeans defining first and second reference positions spaced along a coin path, sensor means for detecting a trailing point on a coin passing the first reference position and a leading point on the coin reaching the second reference position, and processing means for checking the diameter of a coin under test on the basis of said trailing point passing the first reference position and said leading point reaching the second reference position, characterized in that the processing means checks the diameter of the coin under test without reference to said leading point reaching the first reference position. Preferably, the processing means checks the diameter of coin under test on the basis of the time difference between said trailing point passing the first reference position and said leading point reaching the second reference position.
In some embodiments of the present invention, the diameter checked is the physical diameter of a coin under test. However, in other embodiments the diameter is checked on the basis of characterising signal representative of a property related to diameter but dependent also on additional factors such a the material from which a coin under test is made. The reference positions will, in practice, generally have a non-infinitesimal dimension in the direction of coin travel.
Thus, as the diameter-related characteristic determination is based on the time of a coin leaving the first reference position, there is no need for the run-in required by the prior art. Indeed, the first reference position can be located such that a coin extends across it even before a coin is fully in the validator.
As a result of friction between a coin under test and the walls of the passageway and other factors, the speed of a coin passing through the optical beams is indeterminate and some correction for this is normally required. However, if the gap between the reference positions is the same as the diameter of a coin of interest, no correction is required. This is because, for a valid coin, the trailing point leaves the upstream reference position at the same time as the leading point enters the downstream reference position, regardless of the speed of the coin. Therefore, in one preferred embodiment, the reference positions are separated by the diameter of a coin type to be accepted by the validator. Additional reference positions could be added, each spaced from the first by the diameter of a coin type to be accepted. However, if more than a few denominations of coin are to be accepted, the complexity of this arrangement becomes undesirable.
In order to avoid this undesirable complexity, another preferred embodiment includes means to determine a velocity dependent value for a coin passing the reference positions, wherein the processing means is further responsive to the velocity dependent value for a coin under test to produce the characterising signal.
The means to determine a velocity dependent value may comprise means to determine the time elapsing between the trailing point passing the first reference position and the trailing point passing the second reference position.
However, the use of the first and second reference positions for velocity determination is not ideal if the coin accept gate is only a short distance below the second reference position. In such a case there may be insufficient time to process coin characterizing signals before a decision must be made whether to open the accept gate. In order to overcome this situation, the means to determine a velocity dependent value may comprise a third reference position downstream of the first reference position and further sensor means for detecting said leading point reaching the third reference position, wherein the processing means is responsive to the sensor means to derive said velocity dependent value on the basis of the time difference between said leading point reaching the second reference position and said leading point reaching the third reference position. Thus, all the coin characterizing data is obtained before the coin has passed fully through the last reference position.
Preferably, the processing means produces the characterizing signal on the basis of the result of:       (                  t        1            -              t        2              )        (                  t        3            -              t        2              )  
where:
t1 is the time of trailing point passing the upper first reference position, and
t2 and t3 are the times of the leading point reaching the second and third reference positions.
The trailing and leading points on a coin under test will be substantially on the circumference of the coin with some types of sensor. However, the operation of other sensors means the leading and trailing points will be, located radially inward of the coins circumference with one on either side of a diameter of the coin, which runs perpendicular to the coin""s direction of travel
Preferably, the sensor means comprises a beam of optical radiation crossing the coin path and a detector therefor for each said reference position. More preferably, the coin path has a breadth to accommodate the thickness of a coin under test, a width to accommodate the coin""s diameter, and a length along which coins under test can pass edgewise, wherein the sensor means o includes emitter means on one side of the passageway for directing said beams of optical radiation across the width of the passageway and detectors opposite respective emitter means. If the beams are closely spaced, it is advantageous that adjacent beams shine in opposite directions across the coin passageway. This avoids one beam being detected by the photosensor of another beam.
However, other forms of sensor may be used. For instance, the sensor means may comprise inductive sensors. In a preferred embodiment using inductive sensors, the coin path has a breadth to accommodate the thickness of a coin under test, a width to accommodate the coin""s diameter, and a length along which coins under test can pass edgewise, wherein the sensor means includes an elongate inductor arranged substantially parallel to the width direction of the path and having its winding axis substantially parallel to the direction of travel of coins along the path.
In a further embodiment, the sensor means comprises a piezoelectric element associated with each reference position, the piezo-electric elements being arranged to be stressed by tie passage of a coin to produce electric signals. Preferably, at least one of the piezoelectric elements comprises a flap, arranged to stress a piezo-electric film as a passing coin displaces it.
According to the first aspect of the present invention, there is further provided a method of validating a coin comprising the steps of:
(a) moving a coin edgewise past first and second reference positions, the reference positions being fixed relative to each other, and
(b) determining the time difference between a trailing point on the coin passing the first reference position and a leading point on the coin reaching the second reference; characterized by
(c) checking the diameter of the coin on the basis of said time difference without reference to said leading point reaching the first reference position.
Preferably, a method according to the present invention includes the step of producing a coin velocity dependent value, wherein said velocity dependent value is used to derive the value characteristic of the coin. More preferably, such a method comprises the steps of:
(d) moving a coin edgewise past a third reference position;
(e) determining the time difference between said leading point reaching the second reference position and said leading point reaching the fourth reference;
(f) deriving a value representative of the coin""s velocity on the basis of said time difference.
Preferably, optical sensing means are used to detect a trailing point on the coin""s circumference passing the first reference position and a leading point on the coin""s circumference reaching the second reference. However, inductive sensing means or piezo-electric sensing means could be used for determining said time difference or differences.
In many situations, merely measuring the diameter of a disc will not be sufficient to determine whether it is a valid member of a predetermined set of coin types. Typically, additional information will be derived using inductive sensors. In one type of inductive sensor, a coil is arranged beside the coin passageway, with its axis perpendicular to the plane of a coin travelling along the passageway. These inductive sensors are undesirable for compact coin validators if they are wound in the form of a circle or square because this increases the length required for the passageway. However, reducing the dimensions of the coil in the direction of travel of coins to be tested, produces an unacceptable degradation of performance.
A solution to this problem is the use of so called xe2x80x9cwrap aroundxe2x80x9d coils. Wrap around coils are arranged so that a coin to be tested passes along the axis of the coil. However, these coils cannot be opened for maintenance or rejection of jammed coins. This often necessitates a wider than desired gap through which coins under test pass, reducing sensitivity.
It is also an aim of the present invention to overcome the afore-mentioned disadvantages of prior art validator coil arrangements.
According to a second aspect of the present invention, there is provided a coin validation apparatus comprising means defining a passageway for coins under test, the passageway having a breadth to accommodate the thickness of a coin under test, a width to accommodate the coin""s diameter, and a length along which coins under test can pass edgewise, and an inductive coin sensing station including a coil assembly beside the passageway and arranged to inductively couple with a major face of a coin therein, characterized in that the coil assembly is arranged such that the magnetic field produced thereby is substantially constant across the width of the passageway.
Preferably, the inductive coin sensing station comprises first and second coils opposite each other across the breadth of the passageway and having their axes substantially parallel to the direction of travel of a coin in the passageway past the sensing station. With such an arrangement, the coils can be switched between in-phase and anti-phase modes of operation. This cannot, of course, be achieved using a wrap-around coil.
Preferably, the or each coil is wound in the form of an elongate oval or rectangle on a former of magnetic material which is, at least, substantially as long as the passageway is wide. Advantageously, the or each coil includes an elongate I-section former. However, an E- or C-section former may be used. If the former is E-sectioned, the coil may be wound around the top, bottom or middle arms. If the former is C-sectioned, the coil may be wound around any part.
Preferably, a validator includes shielding means to magnetically shield portions of the or each coil not immediately adjacent the passageway.
The slim shape of the coils employed in a validator according to this second aspect enables a more compact validator to be constructed. Alternatively, the space saved can be used for additional sensors of the same or different types. Since the windings of these coils include portions lying parallel to the coin passageway across its entire width, the magnetic field produced in the passageway is substantially constant across the width of the passageway. Consequently, the response to the passage of a coin, obtained from these coils, is independent of the position of a coin across the width of the passageway. This is particularly advantageous in the case of validators where coins are in free fall past the inductive sensor station because the path followed by a coin cannot be rigidly controlled.
Another advantage of the shape of these coils is that they are easier to screen than the coils used in prior art validators.
It has been found that coils of this type are more linear in their response to passing coins than prior art designs.
According to a third aspect of the present invention, there is provided a coin validating apparatus comprising a coin path having a breadth sufficient to accommodate the thickness of a coin under test, wherein a wall, defining in part said breadth, is repositionable to thereby vary said breadth. Preferably, a cam is arranged to act on said wall for repositioning thereof. More preferably, a sense coil is mounted to said wall for sensing a coin moving along the coin path.
Whilst the different aspects of the present invention provide significant advantages when applied individually, a compact validator, particularly suited to the validation of large xe2x80x9ccasinoxe2x80x9d tokens, can be constructed by applying both the first and second aspects. In such a validator, the inductive coin sensing station is preferably located between the upstream coin sensing station and the or a sequentially first downstream coin sensing station.